XRegExp: JavaScript regex library
XRegExp is an open source (MIT license) JavaScript library that provides an augmented, extensible, cross-browser implementation of regular expressions, including support for additional syntax, flags, and methods.
XRegExp is fully compliant with the regular expression flavor specified in ES3 and ES5, and has been tested with Internet Explorer 5.5–8, Firefox 2–3.6, Safari 3–4, Chrome 1–4, and Opera 9.5–10.5. It uses feature detection for its cross-browser support—no browser sniffing.